[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN OCT 29 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE HAS BEEN ADJUSTED ALONG 54W/55W S OF 13N
ESTIMATED TO BE MOVING W NEAR 15 KT. THIS WAVE IS A LOW
AMPLITUDE FEATURE AND IS DIFFICULT TO LOCATE. THE ADJUSTMENT IS
BASED ON SOME SLIGHT LOW TO MID LEVEL TURNING SEEN IN VISIBLE
IMAGES AND A WEAK CLOUD CLUSTER TRACKED IN HOVMOLLER DIAGRAMS.
REGARDLESS OF THE PSN OF THE WAVE...ASSOCIATED SHOWER ACTIVITY
IS MINIMAL.

A STRONG TROPICAL WAVE IS MOVING QUICKLY THROUGH THE CENTRAL
CARIBBEAN ALONG 72W MOVING W NEAR 20 KT. THIS WAVE REMAINS WELL
DEFINED WITH A LARGE ENVELOPE OF LOW TO MID LEVEL CYCLONIC
CURVATURE NOTED IN THE LOW TO MID CLOUD FIELD...BETWEEN
HISPANIOLA AND SOUTH AMERICA. SHOWERS AND TSTMS REMAIN ACTIVE
WITHIN 240 NM E AND 180 NM W OF THE AXIS. HOWEVER THESE SHOWERS
ARE DISORGANIZED AND THERE IS NO EVIDENCE OF A SFC CIRCULATION
AT THE MOMENT. UPPER LEVEL WINDS ARE ONLY MARGINALLY CONDUCIVE
FOR TROPICAL CYCLONE FORMATION...AND DEVELOPMENT...IF
ANY...SHOULD BE SLOW TO OCCUR.

A TROPICAL WAVE IS ALONG 80W S OF 17N MOVING W 10 TO 15 KT. THE
WAVE AXIS HAS BECOME A LITTLE EASIER TO LOCATE WITH SOME MID
LEVEL CLOUD TURNING BECOMING APPARENT ON SATELLITE IMAGES.
UPPER DIFFLUENCE ALONG WITH LOW LEVEL CONVERGENCE ASSOCIATED
WITH THIS WAVE AND THE ITCZ IS PRODUCING A SCATTERED MODERATE
CONVECTION W OF 76W MOSTLY S OF 15N...INCLUDING PARTS OF CENTRAL
AMERICA.

FOR MORE DETAILS ON THE TROPICAL WAVES REFER TO THE CARIBBEAN
SECTION IN THE DISCUSSION BELOW.

 ...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 8N30W 7N40W 6N48W 7N54W. THE
ITCZ IS FAIRLY ACTIVE E OF 40W...WITH CLUSTERS OF SCATTERED
MODERATE CONVECTION NOTED WITHIN 240 NM N OF THE AXIS. SCATTERED
MODERATE ALSO EXISTS FROM 8N-12N BETWEEN 57W-64W.

...DISCUSSION...
THE GULF OF MEXICO...
A POST-FRONTAL DRIER AND COOLER AIRMASS IS IN PLACE ACROSS THE
GULF OF MEXICO WITH A SFC RIDGE STRETCHED ACROSS THE U.S. GULF
COAST WHERE A FEW HIGHS ARE ANALYZED IN THE RIDGE. LIGHT NWLY
SFC WINDS ARE COMMON EXCEPT FOR SOME WINDS NEAR 15 KT S OF 24N.
THE NRN GULF IS EXPERIENCING CLEAR SKIES WITH OFFSHORE
FLOW...WHILE SCATTERED TO BROKEN COOL AIR OVER WARM WATERS
STRATOCUMULUS CLOUDS ARE VISIBLE S OF 27N. A W TO SWLY UPPER
LEVEL JET OF 70 TO 90 KT ON THE SRN SIDE OF A DEEP TROUGH
ORIGINATING IN ERN CANADA CONTINUES TO ADVECT VERY DRY MID TO
UPPER LEVEL AIR ACROSS THE GULF...ESPECIALLY ACROSS THE ERN
PORTION AND FLORIDA. THE SFC RIDGE WILL SLIDE EASTWARD OVER THE
NEXT COUPLE OF DAYS TURNING WINDS TO THE E AND SE ACROSS THE
AREA. THIS LOW-LEVEL FLOW WILL MOISTEN UP THE AIR SLIGHTLY BUT
FAIR WEATHER IS EXPECTED TO CONTINUE ACROSS MOST OF THE GULF
OVER THE NEXT FEW DAYS.

THE CARIBBEAN SEA...
THERE ARE A FEW AREAS OF ORGANIZED CONVECTION IN THE CARIBBEAN
TRIGGERED BY SEVERAL FEATURES. THE MOST IMPRESSIVE AREA IS IN
THE CENTRAL CARIBBEAN WHERE SCATTERED MODERATE CONVECTION IS
FROM 14N-19N BETWEEN 68W-74W...WHICH INCLUDES THE ISLAND OF
HISPANIOLA. THIS ACTIVITY IS BEING TRIGGERED BY A WELL DEFINED
TROPICAL WAVE ALONG 72W...WITH SOME ENHANCEMENT FROM UPPER
DIFFLUENT FLOW BETWEEN A WEAK UPPER LOW NEAR THE CAYMAN ISLANDS
AND LARGE SCALE RIDGING IN THE ATLC. FOR MORE DETAILS REFER TO
THE TROPICAL WAVES SECTION. AREAS OF UNSETTLED WEATHER ALSO
EXISTS IN THE WRN CARIBBEAN WHERE THE TAIL END OF A WRN ATLC
FRONTAL BOUNDARY IS STATIONARY FROM CENTRAL CUBA TO TO THE NRN
COAST OF HONDURAS. THIS PART OF THE BOUNDARY IS STARTING TO
BECOME STRETCHED OUT AND POSSIBLY BEING PUSHED SLIGHTLY W BY THE
EASTERLY TRADES E OF THE BOUNDARY. LOW-LEVEL CONVERGENCE NEAR
THE FRONT AND UPPER DIFFLUENT FLOW...BETWEEN UPPER RIDGING
ACROSS CENTRAL AMERICA AND THE PRONOUNCED UPPER TROUGHING
EXTENDING S FROM THE U.S. EAST COAST...IS PRODUCING CLUSTERS OF
SHOWERS AND TSTMS WITHIN 180 NM OF THE SFC FRONT. CLUSTERS OF
SCATTERED MODERATE CONVECTION ALSO EXISTS IN THE SW CARIB S OF
14N W OF 74W. THIS ACTIVITY IS ALSO BEING ENHANCED BY UPPER
DIFFLUENT FLOW AS DESCRIBED ABOVE...AND LOW-LEVEL LIFT FROM A
TROPICAL WAVE ALONG 80W AND THE ITCZ. SOME OF THESE TSTMS ARE
AFFECTING PARTS OF COSTA RICA AND PANAMA LIKELY PRODUCING
LOCALLY HEAVY RAINS. THE LAST AREA OF ORGANIZED CONVECTION IS IN
THE SE CARIB S OF 12N E OF 65W...ASSOCIATED WITH THE ITCZ AND
ENHANCED BY UPPER DIFFLUENT AIR JUST SW OF THE STRONG ATLC RIDGE.

THE ATLANTIC OCEAN...
A RATHER STRONG COLD FRONT IS OVER THE W ATLC EXTENDING ALONG
32N68W 28N72W THROUGH THE BAHAMAS AND CUBA. THE NUMEROUS
MODERATE CONVECTION LOCATED E OF THE FRONT EARLIER HAS BEEN
DECREASING OVER THE PAST FEW HOURS TO SCATTERED SHOWERS AND
TSTMS NOW WITHIN 240 NM E OF THE FRONT. BEHIND THE FRONT
...STRONG W/SWLY UPPER LEVEL WINDS ARE ADVECTING VERY DRY AIR
ALOFT INTO THE WRN ATLC. SFC HIGH PRES IS ALSO BUILDING IN
TIGHTENING THE PRES GRAD WHICH IS PRODUCING GUSTY SW FLOW E OF
THE FRONT. A MUCH STRONGER GRADIENT IS WELL N OF THE AREA OFF
THE MID ATLANTIC/NORTHEAST COAST. A LARGE AMPLIFIED MID/UPPER
LEVEL RIDGE EXTENDS E OF THE BOUNDARY CENTERED NEAR 26N56W AND
COVERS THE REGION BETWEEN 40W AND 65W. A SMALL ANTICYCLONE
CENTERED OVER THE SE BAHAMAS IS EXTENDING THE RIDGE WESTWARD IN
THE SW ATLC. DRY STABLE AIR ALOFT IS ASSOCIATED WITH THIS RIDGE.
E OF THE RIDGE...AN UPPER LOW HAS BECOME CUT OFF FROM THE SHARP
TROUGH WITH ITS CYCLONIC CIRCULATION COVERING THE AREA BETWEEN
25W AND 40W MAINLY N OF 25N. AN ASSOCIATED COLD FRONT EXTENDS
FROM 32N31W 27N36W 25N44W THEN STATIONARY TO 25N52W. ONLY
ISOLATED SHOWERS ARE WITHIN 120 NM S OF THE BOUNDARY E OF 38W.
WITH NO SHOWERS NOTED W OF 38W NEAR THE BOUNDARY AS SUBSIDENCE
IS LIKELY SUPPRESSING IT. MUCH OF THE E ATLC N OF 15N BETWEEN
AFRICA AND 40W IS ALSO IN A DRY/STABLE ENVIRONMENT WITH
SCATTERED STRATOCUMULUS CLOUDS. A BROAD UPPER LOW IS SPINNING
JUST N OF THE CANARY ISLANDS WITH AN ASSOCIATED WEAK 1011 MB
SURFACE LOW NEAR THE WRN CANARIES AT 28N19W. AN ELONGATED UPPER
TROUGH WHICH EXTENDS WSW THROUGH THE DEEP TROPICS IS SHEARING
THE HIGH CLOUDS FROM THE ITCZ CONVECTION TO THE E/NE.

$$
CANGIALOSI




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